My answer: DNS is called domain name system, and its main task is to convert the host name that is easy for people to remember into the fixed-length IP address that routers like. DNS resolution only corresponds to IP, not port.

Ports are provided by services.

General DNS resolves domain names, which are composed of various records, such as A record, NS record, MX record and CNAME record. The A record specifies the IP address corresponding to the domain name, and the NS record specifies which server resolves the domain name. MX record is a mail exchange record, pointing to the mail server. CNAME is an alias record.

Generally, by building a webserver, the IP of the website service can be written into the domain name A record, and the website uses port 80 or 443. Similarly, the mail service is port 25, port 1 10, which can be resolved by MX records of domain names.